1. Field of the Invention
The present invention generally relates to high-pressure fluid pumps. More particularly, the present invention relates to the fluid-handling sections, or fluid ends, of such high-pressure pumps.
2. Background Information
High-pressure, reciprocating fluid pumps have been used for many years in a variety of applications including oilfield applications, waterblasting, and the like. Such pumps are employed to pressurize water or other incompressible fluids to pressures upward of 10,000 pounds per square inch (p.s.i.).
These pumps typically employ a plunger reciprocating in a bore of a cylinder to pressurize fluid. Because of the high pressure generated and the reciprocating nature of such pumps, the sealing assemblies and lubrication systems of the pumps are of considerable importance in pump performance. Typical seal or packing assemblies include several seal rings of elastomeric material, which are positioned in the bore by one or more spacer members. See, e.g. U.S. Pat. No. 5,263,987, Oct. 19, 1993 to Harrison, and U.S. Pat. No. 4,991,495, Feb. 12, 1991 to Losgel, Sr. et al. These seals rely in part on frictional engagement between the seal, the plunger, and the bore to establish a seal against fluid leakage around the plunger. Consequently, these seals must be lubricated to prevent excessive friction and the resulting heat buildup. Typical prior-art seal assemblies are lubricated with fluid oils forced into the bore of the fluid end through a lubricant passage. The fluid lubricants include castor oil, brake fluid, and waste lubricants such as used transmission fluid. These lubricants mix with and contaminate the water or other process fluid that is pressurized by the pump.
Increasing environmental regulation restricts the level of contamination of process fluids that is acceptable for a given application. Thus, in many applications, prior-art, forcefully lubricated seal or packing assemblies are impractical. However, most prior-art seal assemblies will not operate satisfactorily if the seals are not lubricated. The friction caused by an unlubricated seal assembly causes temperature increases in pump components and may cause the plunger to seize in the bore of the cylinder.
A need exists, therefore, for an improved fluid end including a seal assembly that does not require forced lubrication with a fluid lubricant, wherein the lubricant does notcontaminate the process fluid to environmentally unacceptable levels.